Image forming apparatus

Abstract

An image forming apparatus has a chassis, a feed roller rotatably supported by the chassis, a feed roller gear relatively unrotatably coupled to the feed roller, a motor that drives the feed roller, a drive gear that receives driving force from the motor, and an intermediate gear having a gear portion that engages the drive gear and the feed roller gear and an axle portion that is rotatably supported to the chassis via intermediate gear bearings. At least one of the intermediate gear bearings includes a substantially circular inner surface and a stepped portion that is depressed from the circular inner surface. The axle portion of the intermediate gear is supported by the stepped portion while the intermediate gear transmits driving force the motor from the drive gear to the feed roller gear during printing.

1. An image forming apparatus comprising:
 a chassis having first and second side plates; 
 a feed roller rotatably supported between the first and second side plates for conveying the paper; 
 a feed roller gear relatively unrotatably coupled to the feed roller; 
 a motor configured to drive the feed roller; 
 a drive gear arranged to receive driving force from the motor; and 
 an intermediate gear having a gear portion that engages the drive gear and the feed roller gear and an axle portion that is rotatably supported to the chassis via intermediate gear bearings, at least one of the intermediate gear bearings including a substantially circular inner surface and an elevated stepped portion that is elevated from the circular inner surface, the axle portion of the intermediate gear being arranged to be supported by the elevated stepped portion while the intermediate gear transmits driving force in one direction of the motor from the drive gear to the feed roller gear, 
 the elevated stepped portion including first and second direction ends and a single inner surface that continuously extending between the first and second direction ends and is formed into a substantially arcuate shape concentric to an outer peripheral surface of the axle portion of the intermediate gear with the outer peripheral surface of the axle portion of the intermediate gear being supported only by the inner surface of the elevated stepped portion, with an inside diameter of the inner surface of the elevated stepped portion being substantially the same as an outside diameter of the axle portion of the intermediate gear, the elevated stepped portion being located in a direction of a resultant force with respect to the axle portion, the resultant force being a resultant force of forces received from the drive gear and the feed roller gear when the intermediate gear transmits the driving force in the one direction of the motor from the drive gear to the feed roller gear, 
 the first and second direction ends of the elevated stepped portion being disposed at two locations spaced from the direction of the resultant force by a specific angle in both circumferential directions of the axle portion of the intermediate gear and are located at different heights from each other that are lower than a rotational center of the axle portion. 
 
   
   
     2. The image forming apparatus according to  claim 1 , wherein
 each of the intermediate gear bearings includes the substantially circular inner surface and the elevated stepped portion that is elevated from the respective circular inner surface, the axle portion of the intermediate gear being arranged to be supported by the elevated stepped portions while the intermediate gear transmits driving force of the motor from the drive gear to the feed roller gear. 
 
   
   
     3. The image forming apparatus according to  claim 1 , wherein
 the axle portion and the gear portion of the intermediate gear are formed unitarily as a one-piece member. 
 
   
   
     4. The image forming apparatus according to  claim 1 , further comprising:
 a resinous side plate member mounted on the first side plate of the chassis and unitarily provided with a feed roller bearing that rotatably supports the feed roller, 
 one of the intermediate gear bearings being formed unitarily with the side plate member. 
 
   
   
     5. The image forming apparatus according to  claim 4 , further comprising
 a motor bracket mounted on the first side plate of the chassis, the motor being mounted to the motor bracket, 
 the other of the intermediate gear bearings being formed unitarily with the motor bracket. 
 
   
   
     6. The image forming apparatus according to  claim 5 , wherein
 the other of the intermediate gear bearings formed on the motor bracket is formed so as to project from the motor bracket. 
 
   
   
     7. The image forming apparatus according to  claim 1 , wherein
 an angular range within which the elevated stepped portion extends relative to the circular inner surface is less than 180°.